[ICEM] mesh periodicity without any periodic boundaries

Will Anderson · November 22, 2010, 17:26

What happens if I declare a 4-sided mesh to be rotationally periodic, but completely bound the mesh on its periodic sides by walls? Furthermore, the wall facing the center of rotation is an inlet and the wall facing outwards from the center of rotation is an outlet.

Do any aspects of the mesh's declared periodicity carry over into Fluent?

Will the mass flow be multiplied by 12x due to periodicity?

PSYMN · November 24, 2010, 12:00

Periodicity is a short cut... Instead of meshing and solving the whole thing, it just takes care of the one segment. It manages this by transposing the flow thru the periodic boundary to the other periodic elements. This is most easily done (without need for interpolation) if the mesh is also periodic. In other words, the flow out the left periodic boundary flows in the right periodic boundary as if the elements were next to each other.

If you put walls along these boundaries, then there is no flow. Are you allowing heat transfer thru these walls? If not, then there is nothing passing thru these walls, so the solver periodicity is meaningless and the mesh periodicity was unnecessary.

As for the inlet and outlet, you determine the format of your results (Line Average, MaxVal, etc.), but I don't think it would be multiplied by default. However, you could use the equation editor to multiply the flow by 12 if that is what you would like to see in the report.

Best regards,

Simon

Will Anderson · November 25, 2010, 03:04

Thanks for the thorough explanation. Nope, no heat transfer over them walls. I was looking for the equation editor which you mentioned but came up empty handed. Any leads?

PSYMN · November 26, 2010, 18:51

I always use the CFD Post tool rather than the Fluent Post... In workbench it is the last field in the Fluent System...

CFD_POST_Schematic.jpg

Once in CFD Post, The 3rd tab lets you create expressions...

CFD_POST_Expressions.jpg

Right click in the top section to create new...

Once in the lower screen, you can right click to choose the expression, variable and location... It is very easy to use. Once you have an expression back in the top window, you can right click on it and promote it to a workbench output parameter for use with optimization or at least keeping track of your parameters.

November 22, 2010, 17:26	mesh periodicity without any periodic boundaries	#1
Will Anderson Member W.N. Anderson Join Date: Jul 2010 Location: Zürich, Switzerland Posts: 46 Rep Power: 15	What happens if I declare a 4-sided mesh to be rotationally periodic, but completely bound the mesh on its periodic sides by walls? Furthermore, the wall facing the center of rotation is an inlet and the wall facing outwards from the center of rotation is an outlet. Do any aspects of the mesh's declared periodicity carry over into Fluent? Will the mass flow be multiplied by 12x due to periodicity?

November 24, 2010, 12:00	unnecessary	#2
PSYMN Senior Member Simon Pereira Join Date: Mar 2009 Location: Ann Arbor, MI Posts: 2,663 Blog Entries: 1 Rep Power: 47	Periodicity is a short cut... Instead of meshing and solving the whole thing, it just takes care of the one segment. It manages this by transposing the flow thru the periodic boundary to the other periodic elements. This is most easily done (without need for interpolation) if the mesh is also periodic. In other words, the flow out the left periodic boundary flows in the right periodic boundary as if the elements were next to each other. If you put walls along these boundaries, then there is no flow. Are you allowing heat transfer thru these walls? If not, then there is nothing passing thru these walls, so the solver periodicity is meaningless and the mesh periodicity was unnecessary. As for the inlet and outlet, you determine the format of your results (Line Average, MaxVal, etc.), but I don't think it would be multiplied by default. However, you could use the equation editor to multiply the flow by 12 if that is what you would like to see in the report. Best regards, Simon

November 26, 2010, 18:51	Expressions...	#4
PSYMN Senior Member Simon Pereira Join Date: Mar 2009 Location: Ann Arbor, MI Posts: 2,663 Blog Entries: 1 Rep Power: 47	I always use the CFD Post tool rather than the Fluent Post... In workbench it is the last field in the Fluent System... CFD_POST_Schematic.jpg Once in CFD Post, The 3rd tab lets you create expressions... CFD_POST_Expressions.jpg Right click in the top section to create new... Once in the lower screen, you can right click to choose the expression, variable and location... It is very easy to use. Once you have an expression back in the top window, you can right click on it and promote it to a workbench output parameter for use with optimization or at least keeping track of your parameters.

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November 25, 2010, 03:04		#3
Will Anderson Member W.N. Anderson Join Date: Jul 2010 Location: Zürich, Switzerland Posts: 46 Rep Power: 15	Thanks for the thorough explanation. Nope, no heat transfer over them walls. I was looking for the equation editor which you mentioned but came up empty handed. Any leads?